“…Crystal field engineering (CFE) has proven to be a highly effective strategy for optimizing the properties of phosphors in a specific material system. 21–24 Based on this approach, researchers have made significant progress in developing and optimizing NIR phosphors, such as AMP 2 O 7 :Cr 3+ (A = Li, Na, K; M = Al, Ga, Sc, In) systems, 16,18,25,26 A 3 B 2 C 3 O 12 :Cr 3+ (A = Y, Lu, Gd, Ca; B = Al, Ga, Sc, In, Mg, Y, Hf, Zr; C = Al, Ga, Si, Ge) garnet systems, 1–3,7,14,27–32 and MM′A 2 O 6 :Cr 3+ (M = Li, Na, Mg, Ca; M′ = Mg, Al, Sc, In; A = Si, Al, Ge) pyroxene-type systems. 33–36 However, the potential for developing new material systems is limited.…”